So, my venerable Sennheiser CX-300s bit the dust a week ago (it's actually just the 3.5mm jack, I'll probably get it repaired at some point) and I was looking for some replacements. After asking around for alternatives, I decided to try the CX-550s, as I had seen them on PlayTrade on Play.com for around £24 - which seemed to be a bargain, seeing as they retail for around double that.

Purchase

I wouldn't normally discuss the purchasing in a review, however when I had ordered from Play.com I discovered why I had paid £24. The CX-550s I received were fakes (I wish I'd taken photos now, but alas I was so annoyed I forgot!).

After emailing backwards and forwards with the supplier, he reeled off a sob-story about a second supplier and offered to replace the fakes with genuine Sennheisers. I accepted the offer, as I did actually want my headphones.

I've just (as in 30 minutes ago - I'm using them right now) got the replacements, and they are genuine Sennheiser 'phones. Result - albeit with more hassle than necessary.

The Headphones

Right, no onto the meat of the review. I've not written one of these before, so bear with me. I mainly bought the 550s as a replacement (and upgrade) for my 300s, and they are just that. I only have the 300s as a comparison point, so I can really only reference those.

After first listening with the standard silicone ear-pieces, I switched over to the double-flanged ear-pieces supplied with the 550s - and they make so much difference in the high- and mid-ranges.

The first thing I did when plugging the 550s into my Zen was turn off the bass boost I had enabled for the 300s, as they seemed to lack "punch" on the bass - no such lack here. The bass is definitely present, but with that lovely, crisp "punch" rather than a flabby "boom".

My Zen ran out of juice at this point, so I switched over to my desktop PC sound rig.

The other thing is the relative clarity in comparison to the 300s. There is a lot more of the high-end; crash cymbals sound crisper and guitars have a lot more "mid" and "squeal", but at the same time sound more concentrated.

In terms of EQ, I'm using about +2dB of 80Hz and +1dB of 2.5KHz on my Benhringer Xenyx 802 mini-mixer, and no software EQ. Sound source is 320kbps mp3 played through AmaroK on Fedora 12 Linux, with an ASUS Xonar Essence STX sound card.

Conclusion

After asking the other half to keep a look-out for them in London in case the PlayTrade seller didn't send my genuine replacements, it seems like the 550s have been discontinued by Sennheiser, which is a real shame. The best alternative I can see on their website are the CX-870/880 range, which are a good deal more expensive than the 550s, even at retail.

If you decide to buy them from a non-mainstream re-seller, be prepared for the worst. I found this forum post extremely useful, and there was also a comparison image (I can't find the URL now ) detailing how to tell the difference between fakes and genuines. The differences as far as I can remember are:

* Cone-shaped driver mesh (genuines should have straight)
* 1mm gap between driver head and main IEM body
* No cable-clip in packaging
* Relatively unprofessional packaging (cables just stuffed into the bottom pouch rather than being cable-tied)
* No flanged ear-pieces

My advice - if you can get them, these are fantastic headphones and a worthy upgrade to CX-300s for a reasonable price.